Known alarm systems provide communication between a central station, or controller, and a plurality of remote transponders connected for two-way communication with the controller. It is known to address the transponder so that each of the individual transponders recognizes its respective address, and thus "knows" when the particular data transmitted from the controller is intended for that specific transponder. The transponder can be used to control associated units such as flashing a light-emitting diode (led), changing the state of a relay, energizing an indicating device (such as ringing a bell or flashing a strobe light), and similar functions provided locally adjacent the addressed transponder. For a background in such alarm/communication systems, see U.S. Pat. Nos. 4,394,655, issued Jul. 19, 1983; 4,470,047, issued Sep. 4, 1984; and 4,507,652, issued Mar. 26, 1985. All three patents are hereby incorporated herein by reference. All three are entitled "Bidirectional, Interactive Fire Detection System", and are assigned to the assignee of this invention.
In previous systems power consumption and related considerations militate against the use of bells at long distances from the control panel. Motor driven bells consume considerably less power than their predecessors of the vibrating type, but do not entirely alleviate the problem. Backup batteries in alarm systems are required by regulatory agencies to be capable of operating bells (and other indicating devices) for a specified period of time at the end of a specified period of power outage (usually 24 hours). That means the battery, now at a lower capacity with respect to the onset of the power failure, is expected to do the hardest job--drive the bell or a strobe light--after its capacity has been lowered by powering the system during the power outage.
When a bell is placed a long distance from the controller, a higher voltage battery is needed (usually 12 or 24 volts), as are larger wire sizes. An alternate method is to have a power supply located in the vicinity of the remote bell, which has its battery charged from a commercial ac power source directly connected to the power supply. In this case the bells are remotely controlled from the controller.
It is therefore a principal consideration of the present invention to provide an alarm system in which a plurality of indicating units, such as bells, horns or strobe lights, can be conveniently and economically energized and run in one loop, with substantially longer conductor runs and smaller conductor wire size, without compromising the system operation.
It is another important consideration of the present invention to provide such a system in which the remote module controlling the alarm-indicating device includes an arrangement for supervising the indicating device itself.
Still another important consideration is to provide such a system in which the alarm-indicating unit is powered from a local energy reservoir, such as a rechargeable battery, but in which the reservoir is replenished from the controller at a very low charging rate.
Yet another important consideration is to provide such a controller and remote module in an addressable alarm system, so that the controller can designate a specific module to sound its associated bell or horn, or flash its associated strobe, and the controller can also recognize the specific remote module which has either a battery malfunction or some anomaly in the circuit of the alarm indicating device.
Another important consideration is to provide a system in which the energy in the indicating device's reservoir (or battery) is not depleted during a power outage, before the indicating device is required to be energized.
Lastly, an important consideration is to provide such a system where the remote indicating device module can be connected to, and share, the communication circuit in an alarm system.